1. Field of the Invention
The invention relates to a power generation plant, which is driven by a wind or water flow, in particular a power generation plant for obtaining electrical power from a running water flow or ocean current or by wind power in the offshore area.
2.Description of Related Art
Immersed power generation plants implemented independently of dam structures, which are driven by the kinetic energy of a water flow, in particular an ocean current, represent a great potential for the exploitation of regenerative power sources. Because of the high density of the flow medium, a low flow velocity of approximately 2 to 2.5 m/seconds may already be exploited to obtain power cost-effectively. Flow conditions of this type may be provided either as a tidal flow or other ocean currents are exploited, which may achieve economically usable velocities in particular in straits. Flows of this type may drive flow power plants, which have a similar design as wind power plants, i.e., rotors having rotor blades are used as the water turbines. However, other water turbine concepts, such as vertical turbines and tubular turbines, are also conceivable. In addition to the area of application of obtaining power from ocean currents, freestanding, immersed power generation plants of this type may also be used in running bodies of water, in which no barrages having water turbines installed therein may be erected because of provisions due to environmental protection or ship traffic.
A fundamental difficulty in the operation of immersed flow power plants is that, in particular in the offshore area, the maintenance is complex. The water turbine and the electrical generator associated therewith must typically be raised above the water level for this purpose. Because of the dependency on the weather conditions and the waves, floating crane systems are disadvantageous for this purpose, so that the flow power plants are often implemented as buoyant units, which have an anchor on the ocean floor or the base of the running body of water. Buoyant units of this type may be designed so that in case of service, it is possible to raise them to the water surface. According to an alternative design, the flow power plant is retained in the flow on a bearing and support structure, in particular a column-shaped configuration, which stands on the ocean floor. If this bearing and support structure is continued up to the water level, it is possible to move the power generation plant vertically on this structure for maintenance. Support and bearing structures of this type typically project beyond the water level and a lift mechanism is associated therewith. In addition to the complex design, it is disadvantageous for this purpose that the structures, which are situated above the water level and just underneath it, may represent hazardous obstructions for ship travel.
Similar problems arise for offshore wind power plants, which are subjected to continuous corrosion by the salt spray atmosphere surrounding them. Maintenance work is already difficult to execute because of the location. In addition, future offshore wind power plants will be implemented as high-performance and large-scale, which in turn places special requirements on lifting systems for maintenance.